1. Field of the Invention
This invention relates generally to an ablation apparatus with an internally cooled electrode, and more particularly to an electrode with a closed looped cooling device positioned in an electrode lumen, and an electrode sidewall port isolated from a cooling medium flowing through the closed looped cooling device.
2. Description of the Related Art
Current open procedures for treatment of tumors are extremely disruptive and cause a great deal of damage to healthy tissue. During the surgical procedure, the physician must exercise care in not cutting the tumor in a manner that creates seeding of the tumor, resulting in metastasis. In recent years, development of products has been directed with an emphasis on minimizing the traumatic nature of traditional surgical procedures.
There has been a relatively significant amount of activity in the area of hyperthermia as a tool for treatment of tumors. It is known that elevating the temperature of tumors is helpful in the treatment and management of cancerous tissues. The mechanisms of selective cancer cell eradication by hyperthermia are not completely understood. However, four cellular effects of hyperthermia on cancerous tissue have been proposed, (i) changes in cell or nuclear membrane permeability or fluidity, (ii) cytoplasmic lysomal disintegration, causing release of digestive enzymes, (iii) protein thermal damage affecting cell respiration and the synthesis of DNA or RNA and (iv) potential excitation of immunologic systems. Treatment methods for applying heat to tumors include the use of direct contact radio-frequency (RF) applicators, microwave radiation, inductively coupled RF fields, ultrasound, and a variety of simple thermal conduction techniques.
Among the problems associated with all of these procedures is the requirement that highly localized heat be produced at depths of several centimeters beneath the surface of the skin.
Attempts to use interstitial local hyperthermia have not proven to be very successful. Results have often produced nonuniform temperatures throughout the tumor. It is believed that tumor mass reduction by hyperthermia is related to thermal dose. Thermal dose is the minimum effective temperature applied throughout the tumor mass for a defined period of time. Because blood flow is the major mechanism of heat loss for tumors being heated, and blood flow varies throughout the tumor, more even heating of tumor tissue is needed to ensure effective treatment.
The same is true for ablation of the tumor itself through the use of RF energy. Different methods have been utilized for the RF ablation of masses such as tumors. Instead of heating the tumor it is ablated through the application of energy. This process has been difficult to achieve due to a variety of factors including, (i) positioning of the RF ablation electrodes to effectively ablate all of the mass, (ii) introduction of the RF ablation electrodes to the tumor site and (iii) controlled delivery and monitoring of RF energy to achieve successful ablation without damage to non-tumor tissue.
RF ablation electrodes tend to impede out when used at higher power levels. The tissue adjacent to the electrode surface tends to char. There have been numerous cooled electrodes. Examples of cooled electrodes are found in U.S. Pat. Nos. 4,290,435; 4,140,130; 4,881,543; 5,334,193; 5,342,357; 5,348,554; 5,423,811; 5,423,807; 5,437,662; and 5,462,521.
There is a need for an ablation apparatus with a closed loop cooling device positioned in an electrode lumen. There is a further need for an ablation apparatus with a closed loop cooling device positioned in an electrode lumen, and an electrode sidewall port isolated from the closed loop cooling device and suitable for the introduction of probes and/or infusion solutions into a selected tissue site.
Accordingly, it is an object of the invention to provide an ablation apparatus and method with an ablation electrode that does not impede out.
Another object of the invention is to provide an ablation apparatus and method with a cooled ablation electrode.
Yet another object of the invention is to provide an ablation apparatus and method with a closed loop cooled ablation electrode.
A further object of the invention is to provide an ablation apparatus and method with a closed loop cooled ablation electrode and an electrode sidewall port that is isolated from a cooling medium flowing through the ablation electrode.
Still another object of the invention is to provide an ablation apparatus and method with a closed loop cooled ablation electrode, an electrode sidewall port isolated from a cooling medium flowing through the ablation electrode and a probe with a sensor that is advanced in and out of the sideport.
Another object of the invention is to provide an ablation apparatus and method with a closed loop cooled ablation electrode, an electrode sidewall port isolated from a cooling medium flowing through the ablation electrode and an infusion medium introduced into a selected tissue site through the sidewall port.
These and other objectives are achieved in an ablation apparatus that has a handpiece, an electrode extending from a handpiece distal end, a probe, a thermal sensor and an energy source. The electrode includes a distal end, a lumen, a cooling medium inlet conduit and a cooling medium exit conduit. Both conduits extend through the electrode lumen to an electrode distal end. A sidewall port, isolated from a cooling medium flowing in the inlet and outlet conduits, is formed in the electrode. The probe is at least partially positionable in the electrode lumen and configured to be advanced and retracted in and out of the sidewall port. The thermal sensor is supported by the probe. The electrode is coupled to an energy source.
The present invention is also a method for creating an ablation volume in a selected tissue mass. An ablation device is provided that has a handpiece, an electrode, a probe and a thermal sensor supported by the probe. The electrode includes a distal end, a lumen, a cooling medium inlet conduit coupled to a cooling medium outlet conduit which both extend through the electrode lumen to the electrode""s distal end. A sidewall port is formed in a sidewall of the electrode and is isolated from a cooling medium flowing through the electrode. The electrode is inserted into the selected tissue mass. At least a portion of the probe is positioned in the electrode after the electrode has been inserted into the selected tissue mass. A distal end of the probe is advanced from the aperture into the selected tissue. At least a portion of an electrode ablation surface is cooled. Electromagnetic energy is delivered from the electrode to the selected tissue mass. Temperature is measured at a site in the selected tissue mass, and an ablation volume is created.
As electromagnetic energy, including but not limited to RF, is delivered to the selected tissue site, the tissue interface adjacent to the electrode can begin to char and conductivity through the tissue decreases. With a cooling medium the tissue interface remains at a temperature suitable for the delivery of electromagnetic energy to the periphery of the desired ablation site. While a cooling medium is flowing through the electrode, one or more probes, with associated sensors, are deployed into the desired ablation site. The ablation is monitored and controlled. Sensors can be positioned not only at the distal ends of the probes but also at intermediate positions. This permits monitoring of the ablation process between the electrode and the periphery of the targeted ablation volume.